This invention relates generally as indicated to an aircraft fluid delivery device and, more particularly, to a delivery device that boosts low pressure aircraft engine bleed air to supply high pressure fluid to an on-board pneumatic system.
An aircraft will typically include one or more pneumatic systems which are necessary for proper operation during flight. For example, pneumatic deicers installed on the aircraft""s wings commonly need a supply of high pressure fluid so that they may rapidly inflate and deflate to remove accumulated ice. To this end, a fluid delivery device is provided to boost low pressure aircraft engine bleed air so that a rapid series of high pressure fluid pulses can be supplied to the pneumatic system.
The present invention provides an aircraft fluid delivery device having a longer life, increased reliability, faster speed, and/or improved performance when compared to conventional delivery devices. More particularly, the present invention provides an aircraft fluid delivery device comprising a piston assembly, a pilot assembly, and a control assembly. The pilot assembly pilots the piston assembly and the control assembly controls the pilot assembly. Specifically, the control assembly includes non-contact proximity sensors that sense the position of the piston and a controller that controls the pilot assembly, and thus the piston assembly, based on information received from the sensors.
The piston assembly includes a chamber having a low pressure inlet and a high pressure outlet and a piston, which compresses fluid received through the low pressure inlet and exhausts the compressed fluid through the high pressure outlet. The chamber comprises a first chamber portion, which includes an inlet/outlet to the pilot assembly, and a second chamber portion, which includes the low pressure inlet and the high pressure outlet. The piston comprises a first piston portion, which travels within the first chamber portion and a second piston portion, which travels within the second chamber portion. The first chamber portion and the first piston portion have a greater cross-sectional area (e.g., larger diameter) than the second chamber portion and the second piston portion.
The pilot assembly comprises a casing, a poppet within the casing, and a solenoid that is energized to move the poppet from a first position to a second position. When the poppet is in the first position, the pilot assembly defines a first flow path from a low pressure inlet to a vent and, when the poppet is in the second position, the pilot assembly defines a second flow path from the low pressure inlet into the piston chamber. During a return stroke of the piston, the solenoid is not energized so that the poppet is in its first position and fluid from the pressure side of the chamber may vent through the first flow path. During a compression stroke of the piston, the solenoid is energized so that the poppet is in its second position and fluid is introduced into the pressure side of the chamber.
The pilot assembly can include an ejector, which produces a vacuum to suction fluid from the chamber during a return stroke of the piston. The ejector defines a passageway from the low pressure inlet to the vent, including a narrow portion adjacent the low pressure inlet, a wide portion adjacent the vent, and an orifice therebetween. An inlet port from the chamber to the passageway is positioned just upstream of the orifice. When the poppet is in its first solenoid-not-energized position, a vacuum is produced when fluid passes from the narrow portion through the orifice to the wide portion, whereby fluid is suctioned from the piston chamber and flows through the inlet port into the passageway. When the poppet is in its second solenoid-energized position, the ejector""s passageway is blocked and fluid flows therearound to fill the piston chamber.
To turn off the fluid delivery device of the present invention, its electrical power supply must simply be terminated. Upon termination, the solenoid will remain in a de-energized state and the poppet will remain in the first position, regardless of the status of the sensors. The low pressure inlet fluid need not be shut off (as is required with conventional aircraft fluid delivery devices) and can continue to be supplied to the pilot assembly so that ejector can produce a vacuum to maintain the piston at the end of its return stroke. Once the electrical supply to the device is switched back on, the solenoid is energized and the piston begins a compression stroke.
The use of non-contact proximity switches and/or the ability of the fluid delivery device to be turned on/off electrically results in less wear-related damage, thereby providing a longer life and increased reliability. Additionally or alternatively, the ejector""s generation of a vacuum in the piston chamber during the return stroke of the piston accelerates venting, thereby providing faster speed and improved performance.
These and other features of the invention are fully described and particularly pointed out in the claims. The following descriptive annexed drawings set forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative of but one of the various ways in which the principles of the invention may be employed.